Flame retardants have been widely employed in various industrial products such as electrical home appliances and electronic equipment. However, such use of flame retardants has been found to adversely affect such material characteristics as heat, weather or impact resistance or processing property of the matrix resin; and the added flame retardants are bloomed over a surface of a resin.
In an attempt to ameliorate the above problems, there has been suggested a process which comprises bonding chemically a reactive flame retardant, e.g., bromostyrene compound, to a polymer backbone.
For instance, a flame retardant acrylonitrile butadiene styrene(ABS) resin can be prepared by either copolymerizing a bromostyrene compound, an aromatic vinyl hydrocarbon and an unsaturated nitrile with a butadiene rubber emulsifier during the preparation of a conventional ABS resin or blending a terpolymer of bromostyrene, aromatic vinyl hydrocarbon and unsaturated nitrile with a conventional ABS resin.
However, the former process still shows disadvantages: it tends to raise the glass transition temperature as well as entail a low production rate and further requires complicated procedures due to an increase in its coagulation temperature.
In the case of the latter process, it often deteriorates the compatibility of the terpolymer with the styrene acrylonitrile (SAN) resin constituting the matrix for the ABS resin, which in turn adversely affects the mechanical properties of the end product. Accordingly, in order to maintain the compatibility, the content of the bromostyrene compound should be lowered and the terpolymer should be of homogeneous random copolymer.
However, lowering the content of the bromostyrene compound may fail to produce the desired flame retardance; and also a homogeneous random copolymer cannot be produced by using a conventional suspension polymerization method due to a large difference in reactivity between the bromostyrene compound and two other monomers, i.e., aromatic vinyl hydrocarbon and unsaturated nitrile.
Consequently, needs have continued to exist for the development of a process for the preparation of a flame retardant styrenic resin capable of eliminating the above deficiencies.